Hereâ€™s a quick sketch of mars from two days ago, i had both my 8â€ and 12â€ scopes set up, to see how they would perform. Unfortunately the seeing was poor to very poor, so i donâ€™t think itâ€™s fair to judge the performance right now.

First thing i noticed was that the contrast between dark and lighter areas on mars is actually even fainter, makes sense i suppose because the 12â€ gathers twice as much light then the 8â€.
In these bad seeing conditions, i could not see more detail on mars with the 12â€ then in the 8â€, so iâ€™ll have to wait for a real comparison!

Very little detail visible on the disk, the few things that i could see were sinus sabaeus and syrtis major on the preceding limb. Also south of sinus sabaeus there was a streak visible, i guess itâ€™s either Noachis or Hellespontus, (i think Carlos will provide the right answer )

Your results don't surprise me. The aperture gain will be more noticeable on deep sky objects or details on the moon where the objective area fills the field of view. Planets will show a more modest increase in detail (at least that is what happens to me) but the color is enhanced (function of light gathering that reaches your eye). Have fun. Using the Denks??